this is a huge topic, a lot could be said about it, you probably want to get a good book on the subject!
but i will say that it is difficult to have a specific recipe with exact ratios, due to how different the soil and clay is in different places. not all soil and clay are the same, so the ratios need to be figured out as you get your specific materials that you would be working with.
one would do a lot of test samples, write down each specific recipe, and then see which one works best. also you would want a stiffer mixture for the bottom layers, and a finer layer on the top, sometimes with many layers in between.
so it depends, basically, on what kind of soil and clay you have. there are also a lot of different ways to go about it, and many kinds of sealants and finish treatments.
here is a little book i found for free online
an read before, just googled it again....
in there somewhere is some info about making earth floors and testing your soil